WA pace star Jhye Richardson snared three wickets to help skittle South Australia for 128 before Cameron Green helped the Warriors overcome some early batting wobbles in the rain-affected Sheffield Shield clash at the WACA Ground.
The entire morning session on Wednesday was washed out by rain, but WA made up for lost time when play finally began by producing a devastating bowling performance on a juicy wicket.
Richardson finished with 3-22 from 11.3 overs while Lance Morris took 3-25 from eight overs to put WA in the box seat.
Jake Carder top scored for SA with 37, but no other batsman was able to pass 20.
In reply to SA's paltry total, WA were in strife at 2-17 after opener Sam Whiteman fell for a duck and veteran Shaun Marsh was dismissed for 11.
But Green (17no) and Cameron Bancroft (13no off 65 balls) safely guided the Warriors to 2-42 before bad light stopped play late in the day.
Green is vying for a spot in the Ashes and is keen for a big knock after returning scores of nine, seven, 13 and five in his four most recent knocks for WA.
Those low scores came after he scored 106 against South Australia in the Shield opener last month.
"We're definitely still in the game," Carder said.
"It was nice to get some time out in the middle. I was disappointed that I didn't go on with it.
"When I got out I was the only recognised batsmen left, so it was disappointing."
SA openers Jake Weatherald (four) and Henry Hunt (10) both fell cheaply to leave the Redbacks at 2-23.
But the biggest collapse came after the Redbacks had moved to 2-41, with the visitors losing 3-0 in a catastrophic period, which included the loss of dangerman Travis Head for nine.
"We won a good toss today," Gannon said.
"There can be pressure on a bowling group to take wickets when you see a green surface like that.
"When you've got people like Jhye Richardson and Lance Morris bowling rockets, and some control with myself, Joel (Paris) and Greeny at the other end, it's a pretty well balanced attack."
Australian Associated Press